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Fewer trees for the chop?

A walk around Masterton’s streets – and it’s no doubt the same in other Wairarapa towns – shows that butchering trees unnecessarily is a popular hobby.

But it’s one that, at least within private properties, could now come under closer scrutiny.

Last month, the Natural and Built Environment Bill, part of the reformed Resource Management Act, passed its third reading. Through the National Planning Framework, councils would be required to have an oversight of urban trees and stop the free-for-all chopping down of trees on private land.

Unfortunately, this yet-to-be-passed legislation will not, with the best of wills, be operational for 18 months or so, which could encourage frantic chainsaw activity in the meantime. As well, a less environmentally-friendly government could scrub this important initiative entirely.

When urban tree protection was removed by the National Government in 2013 there was widespread removal of trees with self-styled ‘arborists’ door knocking at random with no more than a chainsaw and step ladder.

There was a time when, if a large tree was overhanging a house, qualified arborists would recommend ways of pruning dangerous branches with sensitive pruning, which requires specific skills so the tree could stay to shade many more summers. Now, while the NZ Arboricultural Association backs comprehensive training courses, it seems they are not essential.

One research project in Auckland’s Waitemata board area showed that, over a decade, 60 percent of removals on private land had not been replaced by anything – no buildings, driveways – just gaps where trees had been. This meant that the tree cover in the country’s largest city – where it is needed the most – has been drastically reduced.

There are numerous aesthetic and climate change reasons why urban areas need more not fewer trees. Even the most passionate climate denier will likely peer over the top of his or her rabbit hole and admit that trees provide very real visual appeal and enhance a streetscape.

Then there’s air quality. For every 10 per cent increase in urban tree canopy, ozone is reduced by 3-7 per cent.

As well, trees remove carbon from the air, sequestering it as cellulose in trunks, branches and leaves. As old as nature itself, trees are still one of the most cost-effective ways to remove carbon dioxide from the atmosphere. Research shows a 60 percent reduction in particulates – solid carbonaceous material – from car exhaust fumes when streets are lined with trees.

Trees also have a positive impact on skin cancer, asthma, hypertension and other stress-related problems by filtering out polluted air.

The value of trees during storms was shown dramatically in Auckland earlier this year. For every 5 per cent of tree cover in a city or town, stormwater runoff is reduced by 2 per cent. While pipes can’t be built big enough to handle the extra water, a mature tree absorbs up to 40 per cent of the rain falling on it during a major storm, so a significant amount of water never reaches the ground.

As we enter what’s likely to be a record-breaking summer, it’s worth remembering that trees reduce temperature by shade and transpiring water. Studies have shown that one mature tree can produce the same cooling effect as 10 room-sized air conditioners. They significantly reduce hot spots in cities and can reduce local energy consumption by up to 10 per cent.

Roger Parker
Roger Parker
Roger Parker is the Times-Age news director. In the Venn-diagram of his two great loves, news and sport, sports news is the sweet spot.

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